On a motor vehicle a plurality of electronic control units (hereinafter termed the ECU's) are mounted by each object and function of control. As a means for exchanging information between the ECU's, a serial data communication device has been known (for example, a device disclosed in Japanese Patent Laid-Open No. Sho 62-237895).
The ECU's are interconnected by a serial data link, so that each ECU will be able to utilize data inputted by other ECU, thereby dispensing with duplex wirings between each ECU and each sensor in order to decrease the number of wirings.
However, since the ECU's are connected by wiring harness, there will occur such a disadvantage that if information are exchanged at a high speed between the ECU's, there arises a radiated noise which will affect a car radio, TV, etc. It is, therefore, difficult to reduce noise without decreasing the communication speed. Besides, there is a problem of an effect of external noise, the prevention of which will be required.
To perform serial data communication between the ECU's, a power source circuit and an input/output circuit are required between the ECU's, which, therefore, will be demanded to be decreased in overall weight and size because of a limited mounting space.
In view of the above-described problem, the present invention has been accomplished and has as its object to provide a control module cluster unit capable of constituting a highly reliable vehicle control system for motor vehicles which is capable of high-speed data communication between the ECU's while restraining the effect of noise.